1. Field of the Invention
The present invention relates to an adjusting apparatus of a stereoscopic camera and more particularly to an adjusting apparatus for adjusting a brightness difference between a pair of stereoscopic images.
2. Discussion of prior art
Generally, a stereoscopic image processing in which a pair of cameras take a picture image of an object from different positions, respectively and a distance to the object is obtained from a parallax between two cameras on the paired picture images based on a position where the cameras are installed and parameters such as a focal distance of the camera according to the principle of a triangulation, is known.
In this stereoscopic image processing, the parallax between two cameras with respect to the object is obtained when two image signals are overlapped and coincide with each other, while two image signals are shifted one by one. It is preferable that there is no deviation except for the parallax between two images and it is required that the balance of optical characteristics and the balance of signal characteristics are secured between those two cameras.
In Japanese Patent Application No. Toku-Kai 2001-69402, the applicant of the present invention proposes a technique in which the brightness balance between respective images of the stereoscopic camera is adjusted by correcting a gain of an amplifier so as to minimize the difference between a first evaluation value representing a magnitude of overall brightness of a first window provided in one image of the stereoscopic camera and a second evaluation value representing a magnitude of overall brightness of a second window provided in the other image of the stereoscopic camera.
However, generally, the two cameras constituting the stereoscopic camera have dispersions in their characteristics respectively and have a different direct current component in output signals of the respective cameras. As a result, sometimes a black level which is a reference value in processing images disagrees between the paired image signals. The disagreement of the black level means that the respective images after A/D conversion have a different brightness level and there is a brightness offset deviation between images. The brightness offset deviation can not be deleted by simply adjusting gains of an amplifier as the prior art does and this has been an obstacle in enhancing the accuracy of stereoscopic image processing.